Strategies for supercritical fluid extraction of polar and ionic compounds

The methods used to facilitate the supercritical fluid extraction (SFE) of polar and ionic compounds are based on two general principles, either increasing the polarity of the supercritical fluid (SF) (usually CO2) used as extractant or reducing the polarity of the analytes to be leached from the solid matrices. Changes in the pressure and temperature of the SF, the use of SFs more polar than CO2 or of modified CO2, ion pair formation, esterification, the use of and organometallics, or complex formation are the most common ways of increasing the extraction efficiency for polar and ionic analytes.